What is the motivation behind writing your article, OP, because reading the initial post it seems reasonable(ish) but reading some of your later comments you seem to be mostly moaning that... well I'm not entirely sure.
My experience of part-time working is that of my mum back in the 70s (school hours, good pay because she had a very good trade) and the part-timers i championed to be allowed to work part time post maternity leave in a company i worked for. Mixed experience there.
One reduced to 6 hours a day - 8 until 2 and she came in 10 minutes before her start time, got her PC up and running, collected her coffee and worked like a trojan until time to go. (accounts team and she did manage, through begging and cajoling her in-laws to babysit) to work extra hours for month end closing.
One reduced to 4 hours a day, rolled in 2 minutes before she was due to start, got coffee, started her PC and chatted her way through her 4 hours, working ok but not really pushing it, and moaned constantly that the first one was promoted but she wasn't, that she didn't earn enough that she never had time to shop and to me (her team leader) that it was ok for me since my kids were big and i could go out in the evening to work events etc etc (no mention that i had worked 40-50 hours and more a week the entire time since my oldest was 3). She flatly refused to change her hours a bit for month end closing (despite her husband having said that he would be available for the children). She was also constantly off with a sick child (3 small ones, it's understandable but she NEVER EVER thanked us for picking up all her slack all the time)
So it's swings and roundabouts and requires the employees and the employer to have clear expectations of how it will work. (TBH this also needs to be done for full-timers but it is a slightly different issue there, i think)
General consensus seems to be that part-time workers can be very efficient and effective and that it can be a benefit to everyone involved. But it requires effort and some companies and some employees aren't prepared to put that in.
Also my experience: my friends who got a way up the career ladder and then went part-time are more satisfied than those who didn't.